Com base no meu entendimento, aqui está a consulta que eu faço:
SELECT name, membersCount, IFNULL(totalCount, 0) goalsCount FROM
(
SELECT m.team_id, SUM(innerQuery.goalsCount) totalCount
FROM (
SELECT m.id memberId, COUNT(*) goalsCount
FROM Members m
JOIN Goals g
ON m.id = g.member_id
GROUP BY member_id
) innerQuery
JOIN Members m
ON innerQuery.memberId = m.id
GROUP BY m.team_id
) inner_1
RIGHT JOIN
(
SELECT t.id, t.name, COUNT(*) membersCount
FROM Teams t
JOIN Members m
ON t.id = m.team_id
GROUP BY team_id
) inner_2
ON inner_1.team_id = inner_2.id
A divisão da consulta:
#1. Obtenha o ID do membro com a contagem de metas associadas (innerQuery)
SELECT m.id memberId, COUNT(*) goalsCount
FROM Members m
JOIN Goals g
ON m.id = g.member_id
GROUP BY member_id
#2. Obtenha o ID da equipe com a SOMA total das metas (inner_1)
SELECT m.team_id, SUM(innerQuery.goalsCount) totalCount
FROM (
.... Sub-query in step 1
) innerQuery
JOIN Members m
ON innerQuery.memberId = m.id
GROUP BY m.team_id
#3. Obtenha a contagem total de membros por equipe (inner_2)
SELECT t.id, t.name, COUNT(*) membersCount
FROM Teams t
JOIN Members m
ON t.id = m.team_id
GROUP BY team_id
#4. RIGHT JOIN inner_1 e inner_2 (já que haverá NULL) e use IFNULL para verificar e substituir esse 0
SELECT name, membersCount, IFNULL(totalCount, 0) goalsCount FROM
(
.... Sub-query in step 2
) inner_1
RIGHT JOIN
(
.... Sub-query in step 3
) inner_2
ON inner_1.team_id = inner_2.id
